MOAB, UTAH — A pack of ravenous but hopelessly trapped Utahraptors, a pair of besieged “horse dragons,” and even a cannibalized baby are among the victims that Utah’s state paleontologist sees immortalized in a fossilized “dinosaur death trap” discovered near the town of Moab.

And despite the fact that years — perhaps decades — of work lay ahead in carefully removing the fossils from their rocky tomb, a detailed picture is already starting to emerge of how this bizarre prehistoric pileup came to be, and what surprising revelations it may hold.
Utahraptor ostrommaysorum (Emily Willoughby)

“Last year was my 40th anniversary of chasing dinosaurs on the Colorado Plateau,” he told Western Digs. “And in 40 years, this is probably the most significant single fossil, as a block, that I’ve ever tried to collect. And I’ve named 20 dinosaurs.”

For one thing, he said, both predator and prey include specimens that seem to cover a wide range of ages and sizes — possibly both family groups.

Among the predators, at least six Utahraptors have been tentatively identified, he said: two adults, each 5 to 6 meters in length; three juveniles about the size of turkeys; “and one that’s tiny, a little bitty baby with all the teeth in it — beautiful.”

And some of the remains testify to the grim end they met. “The leg of the baby clearly has tooth marks in it. So we think some of the utahraptors were also being scavenged [after they were trapped].”

The rock deposits themselves are also giving up clues about how the deadly trap first formed. The fossils are embedded in densely packed “blobs of fine sand,” Kirkland said, surrounded by layers of clay in which there are no fossils at all. The pattern suggests that it was quicksand — not mud — that trapped the ancient animals.

“You wouldn’t sink out of sight like in the old Tarzan movies, because you’re still more buoyant than sand mixed with water,” he said. “But you could get bogged in and trapped, so that you can’t get out and you die, or predators can come and finish you off.”
The herbivorous Hippodraco may have been the prey in Utah’s dinosaur death trap (PLoS ONE)

What drew the raptors into the sandy trap in the first place was a pair of plant-eaters, one large and one small, perhaps a parent and offspring, he said.

The possibility of finding different dinosaur species of different ages raises all in one collection raises tantalizing prospects for learning how dinosaurs developed and reared their young.

“This thing is gonna tell us about the growth history of these animals, and potentially there will be data that can be translated into behavioral information,” he said.

But first, scientists have to get the specimens to a lab.

The deposit was found high atop a talus slope at the foot of a cliff. Even though the team has carefully divided the cache of fossils into five separate blocks — four weighing about a half-ton each, and one five-ton behemoth — the packages are too heavy to move down the slope without serious risk of damage.
Paleontologists at the scene of the ‘death trap,’ with fossil blocks covered in plaster (Courtesy James Kirkland)

Kirkland’s best-case scenario, he said, is using a skycrane helicopter to carry the blocks away. But the nearest copter is at a Nevada Air Force base, and the federal government prohibits military equipment from being used for tasks that can be handled by the private sector, he said.

And even if he could find one that’s flown privately — like those used in the logging industry, for example — the rigs can cost as much as $12,000 an hour.

Another option is to slide the blocks downhill. A local contracting company has donated highway guardrails that could be used as skids, Kirkland said, but “the airlift would be the most gentle on the specimens.”

In either case, Kirkland’s team has until winter to find a solution. Although the death-trap site is on state land, the Bureau of Land Management controls the road that leads to it, and BLM offiicials have said they intend to permanently close the road in five months.

Despite all of these frustrations, Kirkland said he’s determined to get the historic find to the safety of the Utah Musuem of Natural History in Salt Lake City, where he, his team, and students at the University of Utah can begin unpacking its secrets.

“I don’t think any site after this will have as much information as this site has,” he said. “Some of [what we’ll learn from it] may shock me, and I named Utahraptor. It’s my baby.”